1. Field of the Invention
The present invention relates to the implementation of telecommunications services within a plurality of telecommunications networks and, more particularly to a system, method and apparatus for providing a subscriber feature supported by a first telecommunications network to a mobile subscriber traveling within a second telecommunications network.
2. Background and Objects of the Present Invention
With the advent of mobile telecommunications networks, subscribers are able to travel freely within a particular service area and still enjoy the same telecommunications features and services associated with his or her home telecommunications service provider. However, due to a number of incompatible communication protocols and needs, a subscriber may still be assigned with two or more telephone directory numbers. For example, a subscriber may be assigned with a home telephone directory number as well as an office directory number. The subscriber may also be assigned with a mobile or cell number.
Although there is a great need and convenience in assigning and using a single telephone directory number to communicate with a particular subscriber, due to undesirable air-time and call connection charges levied by public telecommunications service providers, mid-to-large size companies and businesses would nevertheless prefer to maintain their own private communication systems. As an illustration, mid-to-large seize companies typically maintain a private branch exchange (PBX) for providing voice communication system within its premises. A subscriber can then establish a PBX call connection with another subscriber within the same PBX system without ever using the Public Switch Telephone Network (PSTN) or Public Land Mobile Network (PLMN). Since no PSTN or PLMN service was used in establishing that PBX call connection, no service charges would be levied against the PBX user by the public service provider.
Furthermore, many companies operate and maintain a local area network (LAN) for providing an independent data communication system within their working environment. Such LAN communication enables multiple users/subscribers to communicate and access Internet/intranet, emails and databases servers.
Furthermore, in order to introduce a converged network to handle all communications within a company, a private mobile telecommunications system also known as “Global System for Mobile System (GSM) on the Net” has been recently introduced. The GSM-on-the-Net is based on International Telecommunications Union ITU-T Recommendation H.323, which describes terminals, equipment and services for multimedia communication over a packet based network. As an illustration, all nodes in GSM-on-the-Net are connected to a corporate Intranet, and communication between the system nodes and radio access nodes providing wireless radio interface to terminals is handled over the Internet Protocol (IP) over the existing corporate Intranet connection. Accordingly, instead of using telephone numbers and separate PBX telecommunications network, the GSM-on-the-Net uses IP addresses and ports to ensure that data and signaling flows are routed to the correct destinations over an existing packet network (LAN).
Reference is now made to FIG. 1 wherein a block diagram of a GSM-on-the-Net is illustrated. For illustrative purposes, the GSM-on-the-Net is used to describe the implementation associated with the present invention. Notwithstanding the above, the present invention can be utilized within any enterprise mobile network and public mobile network. The advantage of the GSM-on-the-Net system is providing mobile telecommunications service over an existing IP network, such as a corporate LAN system. As a result, the same IP LAN system provides the data communication capability, such as emails, database server access, computer networking, etc., as well as providing the voice communications within a particular corporate environment.
As an illustration, a mobile station 10A requests an outgoing call connection while traveling within a GSM-on-the-Net service area 100. This mobile station 10A could be a typical GSM mobile station utilizing the standardized GSM air-interface and associated protocols. However, other mobile stations utilizing different protocols and interfaces could also be applicable in accordance with the present invention. A base transceiver station (BTS) 110 serving a particular geographic location associated with the requesting mobile station 10A then receives the service request and transmits the same to an associated radio network server (RNS) 130. For illustrative purposes, an RNS is similar to a base station controller (BSC) within a GSM or other similar PLMN systems. Since all communication between the BTS 110 and the associated RNS as well as any other elements or nodes within the GSM-on-the-Net system are performed over an existing IP network 120, the serving BTS 110 needs to packetize the received request information from the mobile station 10A. Such an interworking or packetization is required to transport the data over the connected IP connection 120 or 125. Accordingly, an Abis Gateway (Abis GW) 115 associated with the serving BTS 110 reformats and packetizes the received GSM data within an IP packet to be transported over the IP connection 120/125 to the serving RNS 130. The RNS 130, in turn, transmits the call connection request encapsulated within the received IP packet to an associated network access controller (NAC) 140 over an IP connection 135. The NAC performs similar functions as a mobile switching center (MSC) within a conventional PLMN system. The serving NAC 140 then communicates with a connection control node within the enterprise system, also known as a GateKeeper (GK) 150, to request and receive proper call handling instructions for this particular call connection. As an example, if the outgoing call connection request was towards a called party subscriber outside of the GSM-on-the-Net network 100, the GK 150 forwards the call connection request to a gateway (GW) node 200 interfacing the GSM-on-the-Net network with the outside PLMN and PSTN 180 over an IP connection link 165. An SS7 GW 160 within the GW 200 would reformat the IP packet into an appropriate PLMN or PSTN signal, such as an SS7 initial address message (IAM) signal, and forwards it over to the associated VGW 170. The VGW 170, in turn, forwards the received signal over to the associated PSTN or PLMN over its trunk connection 185. As a result, a call connection between the originating mobile subscriber 10B and the called party mobile subscriber 10C is established over two different networks.
On the other hand, if the called party subscriber is another GSM-on-the-Net subscriber being served within the same enterprise network, the GateKeeper (GK) 150 communicates with associated NAC 140, RNS 130, and BTS 110 currently serving that destination mobile station 10B to establish a call connection therebetween.
As illustrated, one of the advantages of the GSM-on-the-Net enterprise system is the capability to provide mobile service within a corporate environment while utilizing the existing IP infrastructure. Accordingly, the same IP infrastructure is also used by the corporation to provide its LAN/WAN capabilities. Furthermore, since this is a private network, a number of enhanced subscriber services and features can further be provided to its members. Such services and features include speed dialing, short dialing, corporate long distance services, conference calls, etc. As the mobile station 10A roams out of the GSM-on-the-Net network and into an existing PLMN 180, the mobile station automatically detects the new service provider and switches over to a particular public service provider currently providing radio coverage over that geographic area. As a result, the mobile subscriber is able to maintain one telephone number as well as one mobile terminal device while freely traveling in and out of its private enterprise network.
However, when the mobile station 10A is outside of its GSM-on-the-Net network 100 and being served by a PLMN 180, all of the features, services, and added securities of the private enterprise network (e.g., GSM-on-the-Net) are no longer available to the mobile subscriber. The mobile station 10A merely functions as a typical mobile station within that PLMN 180 having access to only those services provided therein until the mobile station 10A roams back into the GSM-on-the-Net coverage area.
Accordingly, there is a need for a mechanism to enable a GSM-on-the-Net mobile station to have access to its private enterprise network features and services even when the mobile station is outside of the GSM-on-the-Net environment and being served by a PLMN.